Extraction of pentosans from wheat bran by conventional and combined methods

Wheat bran as a by-product of milling contain various compounds such as pentosans which have health promoting effects and functinal properties in industrial applications. In this study the extraction yield of pentosans by hot water 80oC, 0.01 mM sodium hydroxide and 2% alkaline hydrogen peroxide solutions as the conventional methods for pentosan extraction was evaluated. Then, the effects of pretreatments such as cellulase, ultrasound, autoclave and microwave in the presence of sodium hydroxide and water to increase the pentosan extraction yield were studied. Finally, in order to increase the extraction yield of the pentosans, pretreatments with the highest extraction yield (sonication, cellulase enzyme, hot water, sodium hydroxide, hydrogen peroxide) were evaluated as combined treatments. The results showed that the purity of pentosans extracted with sodium hydroxide was significantly higher than the hot water and hydrogen peroxide solution (p<0.05). Also, among the pretreatments of cellulase enzyme, ultrasound, autoclave and microwave in presence of water or sodium hydroxide, the combination of cellulase-sodium hydroxide and ultrasound-sodium hydroxide treatments resulted in the higher yields. The combined treatment of hot water (80oC)+cellulase enzyme+(0.1%)+ultrasound power (560 w, 2 minutes) and the combined treatment of hot water (80oC)+hydrogen peroxide (4%, pH=11.5) were identified respectively as the best combination factors to maximize extraction yield and pentosans purity from wheat bran.